1. Field of the Invention
The present invention relates to a device for the intraocular transfer of active products by iontophoresis.
2. Discussion of the Background
Iontophoresis is a technique which was proposed in 1747 by Verrati and consists in the administration, in particular of medicaments, into the body through the tissues using an electric field involving a small potential difference. The active electrode, which is in contact with the medicament, is arranged at the site to be treated while a second electrode, intended to close the electric circuit, is placed at another site on the body.
The electric field facilitates the migration of the active products, which are preferably ionized. This technique is commonly used for treating skin diseases, and for this purpose there are a variety of devices available on the market.
Iontophoresis applied to treatment of the eye has been the subject of a number of animal experiments and a few clinical tests, using a variety of devices.
Known devices employ a pad which is impregnated with a solution containing a medicament and is in contact with the surface of the cornea and the sclera. Other devices employ a cup or a pipette. A device employing a cup is, for example, described in American patent U.S. Pat. No. 4,564,016 (David M. Maurice). In this patent, the medicament is administered in quasi-point form through the sclera.
In general, the authors find poor reproducibility in their results, which they attribute either to the existence of differences between the animals which are tested, or to unexplained biological phenomena. Furthermore, some operating techniques involve the use of an active electrode of very small area with a very high current density, which increases the risk of damage caused to the tissues, it being possible for this damage to extend to the presence of burns. This is the case, in particular, with the device described in the aforementioned U.S. Pat. No. 4,564,016, which advocates a current density which is at least 50 mA/cm.sup.2 and may even be as much as 2000 mA/cm.sup.2.
Some experiments have been carried out with alkaline solutions whose high pH results in local tissue damage. For example, the article by T. T. Lam et al. "Intravitreal Delivery of Ganciclovir in Rabbits by Transscleral Iontophoresis" published in the Journal of Ocular Pharmacology 10(3) p. 571-575 (1994) describes the point administration of a solution whose pH of 10.8 is out of the question except in the laboratory.
The article by F. Behar-Cohen et al., entitled "Iontophoresis of Dexamethasone in the Treatment of Endotoxin-Induced-Uveitis in Rats" in the journal Experimental Eye Research, 1997-65 p. 533-545 (October 1997), relates to transcorneoscleral iontophoresis carried out on rats with a view to the treatment of uveitis, that is to say a condition affecting the uvea. According to this technique, the medicament diffuses essentially through the cornea, then diffuses into the eye media.
In practice, owing to the lack of reproducibility of the experimental results generally obtained and, above all, the description of burns and necrosis to the tissue where the iontophoresis devices are applied, transocular iontophoresis has remained at the laboratory stage and has not yet been accepted as a method of treating patients.